When the Brazilian Army and government security forces needed a trusty semi-automatic sidearm, it turned to the proven American Colt M1911A1 pistol. The M1911A1 had long since proven itself the world over and was copied (both legally and illegally) by a plethora of global parties. The original Colt version, the M1911, was debuted in 1911 and chambered for the .45 ACP cartridge, seeing combat actions in World War 1. The improved form, the M1911A1 of 1924, went on to see extensive use in World War 2, Korea, Vietnam (among other conflicts) and still sees action even today in far-off places like Afghanistan and Iraq. Since its inception, over 2 million of the type in varied forms have existed. Due to its in-the-field reliability and inherently tough design, the Brazilians became yet another nation to select the storied M1911A1 as their sidearm of choice, eventually giving birth to the "Pistola 9 M973" by IMBEL. Local manufacturing of the M973 began in 1973.

IMBEL (Industria de Material BELico do Brasil) of Sao Paulo, Brazil, began life in 1975 as a state-founded organization but its origins could be traced as far back as pre-war Brazil in 1934 where some of her early products included manufacturing of German Mauser rifles. Since then, the concern has evolved to become a major weapons developer and supplier to the Brazilian military arms with her major products being small arms and ammunition supply. One of the firm's modern production forays became the license-manufacturing of the legendary American Colt M1911A1 in its original .45 ACP form.

A key difference between the Brazilian Pistola 9 M973 and the original American M1911A1 design was the former's chambering of the universal 9x19mm Parabellum cartridge over that of the latter's .45 ACP round. The smaller cartridge allowed for nine rounds to be stored in the vertical, spring-loaded magazine over that of the M1911A1's seven-round capacity. In essence, the M973 was nothing more than a 9mm copy of the M1911A1. The trigger was single-action in nature and operation of the weapon was of the short-recoil principle. The pistol, as a whole, measured in at 216mm (8.5 inches) with the barrel being 128mm (just over 5 inches) in length. Unloaded weight was a reported 1.01 kilograms. Externally, the IMBEL version differed little when compared directly against the M1911A1, featuring clean lines along the receiver, sturdy checkered grip furniture, a solid trigger system set within an oblong ring and an exposed hammer at the rear. A noticeable prawl overhang was forged over the rear of the pistol grip for a firmer dominant hand hold. The safety mechanism was set to the left-hand side of the gun just above the grip while the ejection port was conventionally set at the top middle of the receiver (as in the Colt). Sights were iron with a rear notch and front post.

By all accounts, the M973 was a sturdy semi-automatic pistol that benefitted greatly from her Colt pedigree. IMBEL also produced another version of the M1911A1 as the "9GC-MD1" beginning in 1989 which featured a higher-capacity 9x19mm Parabellum magazine of 17-rounds. The 45GC-MD1 was similar in scope though chambered for the original .45 ACP cartridge and fitting 13-rounds while being produced by computer-directed machinery as opposed to human-controlled. The 45UC-MD1 and 45UC-MD2 were still further developments of the M973 system, both chambered for the .45 ACP cartridge and designed from the start as more compact forms of the original M1911A1. Key differences between these two were the MD1's shortened barrel and the MD2's perforated muzzle for recoil reduction.